1. Field of Invention
The invention relates generally to an anchor and bearing plate assembly for fastening a membrane or other layer to the deck of a roof or a similar substrate, and more particularly to an assembly of this type whose anchor includes a drill section extending from an auger-type shank section so that the anchor is usable with a deck formed of a material that resists entry therein of an auger and therefore requires a drilled hole in the material to receive the anchor.
2. Status of Prior Art
It is common practice to cover the roof of a building with a layer of thermal insulation formed of pads or panels of lightweight material such as fiberglass or rigid foam plastic. These panels are laid down on the roof deck and covered by a sheet of polyvinyl chloride, or other water-impermeable membrane to protect the layer against water penetration.
Since the roof is exposed to the elements, it may on occasion be subject to high velocity winds as high as 150 miles per hour. Unless the insulation and membrane layer are firmly secured in place, the resultant updraft may blow the layer off the roof. For various reasons, the use of bonding agents to adhere the insulation layer to the deck of the roof is now being replaced by mechanical fasteners which serve to retain the layer in place when strong winds are encountered. The present practice of securing the insulation layer to the roof deck is by means of load-bearing plates of sheet metal which overlie the insulation layer and are bolted or otherwise mechanically fastened to the deck.
Among the patents which disclose load-bearing or stress plates for this purpose are the Giannuzzi U.S. Pat. No. 4,574,551, The Williams U.S. Pat. No. 1,286,862, the Sandquist U.S. Pat. No. 4,074,501 and the Carlson U.S. Pat. No. 4,288,951.
While the usual practice, when a roof deck is covered by an insulation layer, is to face this layer with a thin, waterproof membrane to prevent water seepage into the insulation layer, in many situations, use is made only of a waterproofing layer or membrane to cover the roof deck, in which case the anchor and bearing plate assembly serves to fasten the membrane to the roof deck. The present invention is applicable to both situations.
My prior U.S. Pat. No. 4,763,456 discloses an anchor and stress plate assembly adapted to secure an insulation layer to the deck of a roof formed either of relatively soft or hard decking material. The anchor is provided with a flanged head and a shank whose leading section takes the form of an auger screw having a root which tapers toward the tip and a threading spiralled about the root whose crests are of approximately uniform diameter. When the anchor is turned into pulverizable decking material, the tapered root of the auger screw then acts to pack particles of this material into a dense mass in the region surrounding the screw to enhance the holding power of the anchor.
In hard decking material, a hole must first be drilled therein to receive the auger screw whose root when the anchor is turned in, fits within the hole and whose crests then tap a thread in the hole wall to securely retain the anchor. The stress plate which overlies the insulation layer to prevent uplift thereof has a central depression surrounding an opening defined by a circular series of ratchet teeth. When the anchor is fully turned into the decking material, its head then lies within the plate opening and the flange on the head rests within the depression. The anchor head is provided with a pawl that is deflected by the ratchet teeth when the anchor is being turned in, the pawl engaging the teeth when the anchor seeks to turn out, thereby preventing loosening of the installed assembly. The anchor and stress bearing plate assembly disclosed in my prior U.S. Pat. No. 4,763,456 is usable with soft decking material, such as porous wood and fiber composites known commercially as Tectum. In the case of soft decking material, the auger screw of the anchor turns into this material without difficulty. The same assembly is also usable with hard decking material such as gypsum, plaster board to pre-drill a hole in the material before the anchor to tap this hole to internally thread its wall and thereby retain the anchor in the hole.
The main concern of this invention is with a roof anchor and bearing or stress plate assembly adapted to secure a protective membrane or an insulation layer covered by this membrane to a roof deck or similar substrate made of medium-hard material, such as wooden chip board, structural composite board, water board or oriented wood-strand board. Medium-hard material has sufficient hardness to resist the turning in thereto of an auger type anchor such as those disclosed in my prior U.S. Pat. Nos. 4,763,456 and 4,892,429. Hence to use these anchors with a medium-hard roof deck, it would be necessary to first drill a hole in the deck.
This requirement complicates the installation procedure, for the installer of the assembly would first have to run a drill bit through the medium-hard roof deck before installing the assembly. The amount of time consumed in drilling operations in situations where thousands of assemblies must be installed would add substantially to installation costs.
In my copending application Ser. No. 396,109, there is disclosed a self-drilling anchor having a head adapted to receive a screwdriver or other torque-producing tool, the anchor including an externally-threaded shank section functioning as an auger and a drill section extending from the shank section formed by a pair of opposed cutting blades and a pair of guide blades, each angled relative to a respective cutting blade. When this anchor is turned into a substrate, the cutting blades guided by the guide blades proceed to bore a hole in the substrate, and when the shank section enters this hole, the hole is tapped by the threading of the shank section, thereby retaining the anchor in place.
But while an anchor of the type disclosed in my copending application Ser. No. 396,109 is usable for installation in medium-hard and hard substrates, it is not suitable for use in combination with a stress or bearing plate having a circular series of ratchet teeth surrounding the opening in the plate, for this anchor lacks a pawl to engage these teeth to prevent turning out of the anchor and loosening of the installed assembly.
Of prior art interest in regard to anchors having a drilling section is the patent to Ernst et al., U.S. Pat. No. 4,601,625.